<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <script>
      //手写map
      Array.prototype.myMap = function (fn) {
        let arr = []
        for (let i = 0; i < this.length; i++) {
          arr.push(fn(this[i]))
        }
        console.log(arr)
      }
      const arr = [1, 2, 3, 4]
      arr.myMap((item) => item + 1)

      //手写filter
      Array.prototype.myFilter = function (fn) {
        let arr1 = []
        for (let i = 0; i < this.length; i++) {
          fn(this[i]) ? arr1.push(this[i]) : ''
        }
        console.log(arr1)
      }
      const arr1 = [1, 2, 3, 4]
      arr1.myFilter((item) => item > 2)
    </script>
  </body>
</html>
